Why can't I use statistics.mode(arr) to solve it.

public static int migratoryBirds(List<Integer> arr) {
    Comparator<Long> longComp = Long::compare;
    Map<Integer, Long> countMap = arr.stream().collect(Collectors.groupingBy((Integer i)->i, Collectors.counting()));
    long maxFrequency = countMap.entrySet().stream().sorted(Map.Entry.comparingByValue(longComp.reversed())).
    findFirst().get().getValue();
    Integer key = countMap.entrySet().stream().filter(en -> en.getValue() == maxFrequency).sorted(Map.Entry.comparingByKey()).findFirst().get().getKey();
    return key;
}   

Here is a python solution with O(n + k) time and O(k) space:

def migratoryBirds(arr):
    count = {}
    for n in arr:
        if n not in count:
            count[n] = 0
        count[n] += 1
        
    maxval = max(count.values())
    
    best = []
    for key, val in count.items():
        if val == maxval:
            best.append(key)             

    return min(best)

Here is problem solution in Python, Java, C++, C and Javascript - https://programmingoneonone.com/hackerrank-migratory-birds-problem-solution.html

n = int(input()) arr = list(map(int(input().strip().split(" ")))) d={} for i in arr: d[i] = arr.count(i)

maxfreq = max(d.values())
result = 10000 for i in d: if d[i] == maxfreq: result = min(i,result) print(result)